Cask, composition for neutron shielding body, and method of manufacturing the neutron shielding body

Abstract

A cask includes a trunk body that includes a basket having a square pipe or a plate member forming a cell that contains a spent fuel assembly, and a neutron shield that is formed by filling a composition for neutron shielding between the trunk body and an outer cover surrounding the trunk body. The composition includes a refractory material, a density increasing agent, and a neutron shielding material composed mainly of a polymer.

1. A composition for a neutron shield suitable for a cask, comprising:
 20 mass percent to 55 mass percent of neutron shielding material composed mainly of a polymer; 
 a curing agent of 4 mass percent to 55 mass percent: 
 a refractory material of 5 mass percent to 60 mass percent: 
 a density increasing agent of 5 mass percent to 40 mass percent; and 
 a boron compound of 0.5 mass percent to 10 mass percent, 
 wherein the neutron shielding material, the curing agent, the refractory material and the density increasing agent are included in such amounts that the composition has a specific gravity in a range of 1.62 g/cm 3  to 1.72 g/cm 3 . 
 
     
     
       2. The composition for neutron shield according to  claim 1 , wherein the neutron shielding material composed mainly of a polymer is an epoxy resin. 
     
     
       3. The composition for neutron shield according to  claim 1 , wherein the neutron shielding material composed mainly of a polymer is a hydrogenated epoxy resin. 
     
     
       4. The composition for neutron shield according to  claim 1 , wherein the neutron shielding material composed mainly of a polymer is a hydrogenated bisphenol A epoxy resin. 
     
     
       5. The composition for neutron shield according to  claim 1 , further comprising carbon powder. 
     
     
       6. The composition for neutron shield according to  claim 5 , wherein the carbon powder comprises 0.02 mass percent to 4 mass percent of carbon black. 
     
     
       7. A composition for a neutron shield suitable for a cask, comprising:
 20 mass percent to 55 mass percent of a neutron shielding material composed mainly of a polymer; 
 5 mass percent to 60 mass percent of a refractory material; and 
 5 mass percent to 40 mass percent of a density increasing agents 
 wherein the neutron shielding material, the refractory material and the density increasing agent are included in such amounts that the composition has a specific gravity in a range of 1.62 g/cm 3  to 1.72 g/cm 3 . 
 
     
     
       8. The composition for neutron shield according to  claim 1 , wherein the refractory material is magnesium hydroxide powder. 
     
     
       9. The composition for neutron shield according to  claim 8 , wherein the magnesium hydroxide powder has a particle size of 1.5 micrometers to 15 micrometers. 
     
     
       10. The composition for neutron shield according to  claim 1 , wherein the density increasing agent has a density of 5.0 g/ml or more. 
     
     
       11. The composition for neutron shield according to  claim 7 , wherein the density increasing agent is metal powder. 
     
     
       12. The composition for neutron shield according to  claim 7 , wherein the density increasing agent is metal oxide powder. 
     
     
       13. The composition for neutron shield according to  claim 11 , wherein the density increasing agent is metal powder having a melting point of 350° C. or higher. 
     
     
       14. The composition for neutron shield according to  claim 13 , wherein the metal powder having a melting point of 350° C. or higher is any one of Cr, Mn, Fe, Ni, Cu, Sb, Bi, U, and W. 
     
     
       15. The composition for neutron shield according to  claim 12 , wherein the density increasing agent is metal oxide powder having a melting point of 1000° C. or higher. 
     
     
       16. The composition for neutron shield according to  claim 15 , wherein the metal oxide powder having a melting point of 1000° C. or higher is any one of NiO, CuO, ZnO, ZrO 2 , SnO, SnO 2 , WO 2 , CeO 2 , UO 2 , PbO, and WO 3 . 
     
     
       17. The composition for neutron shield according to  claim 10 , wherein the density increasing agent has a density in a range of 5.0 g/ml and 22.5 g/ml. 
     
     
       18. The composition for neutron shield according to  claim 17 , wherein the density increasing agent has a density in a range of 6.0 g/ml and 15 g/ml.